Friday, January 15, 1999 Published at 11:18 GMT


BBC-Sci/Tech

A taste for meat

The human ancestor ventured out from the trees to the savannah for food

One of the distant relatives of man probably developed a taste for meat much
earlier than thought, according to new research.
Australopithecus africanus, a hominid that lived about three million years
ago, was believed to have eaten a diet much like modern chimpanzees. They
forage mostly in wooded areas for fruits and plant material from trees and
bushes.

Later hominids, on the other hand, looked for food in more open environments
such as grasslands and ate the meat of animals they killed with stone tools.

But after studying the fossilised teeth of Australopithecus, Matt Sponheimer
and Julia Lee-Thorp from the University of Cape Town now think its diet may
have been much more diverse - small mammals that could be caught without
tools may even have been on the menu.

Isotopic analysis



Analysing teeth from Australopithecus africanus revealed a diverse diet
The teeth were subjected to isotopic analysis. This technique relies on the
knowledge that different types - isotopes - of a particular atom exist in the
environment in a specific ratio to each other.

For example, grasses and sedges display a different isotopic ratio of carbon
atoms to that found in the plants typical of woodland areas, like herbs. And
since animals absorb some of the carbon they eat into their teeth, a study of
the isotopic ratio in the enamel should say something about the environment
in which the animals lived.

In the case of Australopithecus, the isotopic content of its teeth is
consistent with a diet that included both the grasses and sedges found on
open savannahs and the woodland plants the creature was supposed to have
dined on exclusively.

Common assumtpions

A pattern of scratching and pitting on the creature's molars also hinted at
meat being a likely source of the unexpected isotopic ratios.

The scientists say the common assumption that our ancestors in the genus Homo
developed their large brains after they began eating the nutrient- and
energy-rich animal foods necessary to fuel the larger brains may now need
reappraisal.

"Our results raise the possibility... that dietary quality improved [through
the consumption of animal foods] before the development of Homo and stone
tools about 2.5 million years ago," writes Matt Sponheimer - also of Rutgers
University in New Brunswick, USA - in the journal Science.